J.McG. Stewart’s scientific contributions

In 1987 and 1988, detailed marine hydrographic surveys were carried out over the Phalen Mine workings in the Sydney Coalfield, Nova Scotia, in order to establish the pre- and post-mining seafloor topographies. After describing the equipment, survey techniques and data processing methodology used, the paper compares the 1987 and 1988 hydrographic data for four survey lines, monitored pre- and post-mining, and presents the preliminary seafloor subsidence values measured over the Phalen I West longwall panel.

In 1987, a detailed marine geophysics survey consisting of precision echosounder and sub-bottom profiling was undertaken to establish the pre-mining seafloor topography over the Phalen mine workings in the Sydney Coalfield, Nova Scotia. If the same survey lines and monitoring techniques are subsequently used to establish the post-mining seafloor topography, a comparison of the two data sets may allow an evaluation of the resultant seafloor subsidence profiles.After a brief review of the progress of the longwall seafloor subsidence monitoring program, the paper examines the marine survey undertaken to establish the pre-mining seafloor topography. In addition to outlining the instrumentation and survey techniques used, the data processing methodology is described and the survey results discussed.

The Cape Breton Coal Research Laboratory is currently undertaking a long-term research program to produce effective prediction techniques and establish safe, site-specific mining guidelines for the undersea longwall coalmine workings in the Sydney coalfield, Nova Scotia, Canada. Preliminary work has identified a variety of instrumentation schemes capable of monitoring seafloor subsidence profiles. However, before embarking on an extensive instrumentation development and monitoring program, it was decided to undertake a detailed examination of archival geophysics data collected since 1978, over the offshore portion of the Sydney coalfield. After a brief introduction to the geological and bathymetric conditions found in the offshore portion, the paper examines the results obtained from the analysis of the archival geophysics data and discusses the further application of geophysical techniques for seafloor subsidence monitoring.